JPS6138985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conveyor-type heat treatment apparatus for automatically soldering electronic components to printed wiring boards, particularly electronic components without lead wires, which have become popular in recent years.

Conventionally, there are the following examples of devices that automatically perform soldering.

That is, there is a hot plate system as shown in FIG.
The parts that are temporarily set and are sequentially conveyed thereon are heated through the circulation belt 1.
The purpose is to heat the solder with the heater 2 and to solder unwelded parts here.

Soldering equipment using this method has an extremely simple structure, so it is cheap and easy to operate. However, because strong tension cannot be applied to the belt, the middle part becomes loose, and as a result, the soldering board follows suit. If warpage occurs or there is foreign matter on the belt surface, the adhesion between the board and the belt will deteriorate, resulting in uneven heat conduction, resulting in uneven solder, making it impossible to obtain a perfect product, and the structure is extremely simple. Therefore, the applicable range of soldering is significantly restricted, and at the same time, it is not suitable for mass production, resulting in high product costs.

This method has many drawbacks, including an extremely poor working environment because no consideration is given to harmful gases generated when the solder melts.

Further, as another conventional example, there is a far-infrared heater system as shown in FIG. A plurality of independent rod-shaped infrared heaters 3, 3 rows are provided in the upper part, and each heater 3, 3 is connected to a temperature controller, so that the temperature can be adjusted individually. The temporarily set components transported on the circulation belt 1 are heated and melted by heat radiation from the heater 3 to be soldered. With this method, the structure is simple and the ambient temperature can be adjusted, so it is possible to solder to a board with a small heat resistance load, and mass production can be achieved to a certain extent. However, since it is difficult to delicately adjust the temperature so that the solder can be melted without thermal damage to any substrate, the applicable range is narrow, and the problem of substrate warping is the same as in the conventional example.

Still another example is a far-infrared panel heater system as shown in FIG. 3 in which the heater 3 in FIG. 2 is replaced with an infrared panel heater 4. An infrared panel heater 4 having a surface of a certain width is placed opposite the belt 1, and the parts carried on the belt 1 are heated and soldered by irradiation with far infrared rays. It is cheap because it is simple, and it is possible to roughly adjust the temperature, but the second
Similar to the example shown in the figure, there is a difficulty in delicately adjusting the temperature in the atmosphere, resulting in poor versatility.

In addition to the above, as a modified example shown in FIG. 3, a panel heater is installed oppositely on both sides of the forward path of the heat-resistant circulation belt to enhance the thermal effect, or a panel heater and a rod-shaped far-infrared heater are appropriately combined, In addition, there are various combined systems (not shown) that incorporate a nichrome wire heater and a far-infrared heater, but all of them are designed to increase the diversity of heat distribution in the heating furnace and to support heat treatment of all kinds of parts. be. In addition, as a means for transporting parts (not shown), a wire is stretched spirally between two rollers that are pivoted in parallel with each other at a certain distance, and the rollers are driven. There is a device in which parts are sequentially transferred by circulating the spirally stretched wire.

However, the biggest drawback of each of the above conventional devices is that they cannot handle various cream solders or boards made of different materials without causing heat damage, and the solder remains at its melting temperature from the beginning until it melts. As a result, the circuit elements not only suffer thermal damage but also undergo thermal distortion, often accompanied by damage such as deformation or cracking. It is required to locally adjust the temperature inside the processing furnace due to the The mainstream was dedicated equipment. In addition, in the above-mentioned conveying means using a spiral wire, the wire and the groove of the roller guiding the wire are not parallel, but are angled, resulting in significant wear of the wire or roller. In addition, the looseness of the entire wire is concentrated on the side of the wire that supports the component, resulting in significant drooping, and furthermore, when it breaks, repairing it is extremely troublesome.

Therefore, the present invention aims to address these drawbacks of conventional devices, to obtain temperature conditions that match the thermal characteristics of various parts, and to improve versatility and productivity.

That is, the main point of the present invention is that a wire conveyor is stretched from a plurality of wire rods across a preheating section, a reflow section, and a cooling section, and by using the wire conveyor, a plurality of conveyors with different speeds can be connected in a plane. In addition, a honeycomb-shaped baffle plate is provided in the middle of the hot air path to even out the heat distribution within the furnace.

The present invention will be described in detail below with reference to an embodiment shown in the drawings. First, a conveyor 9 made of a plurality of metal wires (stainless steel wires) is placed approximately in the middle of the device main body 29 covered with a heat insulating material. The belt is stretched across a large number of pulleys 30 and 31 which are pivotally connected to both left and right ends of the conveyor, and the pulleys 30 and 31 are composed of a group of independent pulleys that individually suspend each line of each conveyor 9. Moreover, one of the pulleys 30 and 31 is used for driving, and a driving device (electric motor) is installed at the lower part of the pulley 30 and the device main body 29.
36 through a relay sprocket 35, and furthermore, the conveyor 9 guides each wire by guide pulleys 32 and 33 pivoted near both ends, and a tension pulley 34 in the middle of the circulation stroke. is applied to apply a constant tension to each wire.

Along the circulation direction of the wire conveyor 9, which is made up of a plurality of wire groups, there are a preheating section A for preheating parts, a reflow section B for melting cream solder, and a reflow section B for melting cream solder. A cooling section C for rapidly solidifying the molten solder is arranged in sequence, and each section will be explained in more detail below. It is partitioned by a heat insulating wall 37, and the heaters 12, 1 near the ceiling in the partition are
2 is provided facing the wire conveyor 9, and the fans 13, 13 are equipped with
A honeycomb rectifying plate 14 is installed in the lower part of the conveyor 9, that is, in the hot air passageway, parallel to the traveling direction of the conveyor 9, so as to preheat the upper surface of the unprocessed parts sent onto the conveyor 9. Furthermore, a plurality of far-infrared heaters 10, 10 and sheathed heaters 11, 11 are respectively attached to the lower surface of the conveyor 9 along the traveling direction of the conveyor 9, so that the lower surface of the unprocessed parts is mainly heated. I try to heat it directly.

Next, the reflow section B is connected to the wire conveyor 9.
The upper and lower parts of the conveyor 9 are partitioned by a heat insulating wall 38 to block heat from entering and exiting, and a fan 18 and a heater 24 similar to those used in the configuration of the preheating section are installed in the upper part of the conveyor 9 inside the conveyor 9. A honeycomb-shaped rectifying plate 16 and a far-infrared heater 17 similar to those described above are installed facing the conveyor 9 at the lower part thereof, and a far-infrared heater 15 is installed below the conveyor 9. It is something that has been set.

The fan 18 is attached to the established motor shaft end via the heat dissipation fin 43 on the ceiling, and is attached to the reflow part B.
This protects the motor from internal heat.

Furthermore, the cooling section C includes a bulkhead plate 2 that guides the cold air taken in by the blower fan 19 located at one end of the device main body 29 (the right end in FIG. 7) to the lower part of the conveyor 9.
0 to form a ventilation path a that blows downward obliquely from the guide plate 42 and an upward ventilation path b.

Then, a Morotsuko fan 21 for gas exhaust is installed on the upper surface of the device main body 29, and dampers 38', 3 of the Morotsuko fan 21 and the duct ports 38, 39 opened in the preheating section A and the reflow section B, respectively.
9' and the cold air ventilation path b are connected through a duct 22 to completely exhaust harmful gases in the atmosphere. Note that the circuits of all of the heaters in the preheating section A and the reflow section B are configured so that their respective temperatures can be adjusted individually by a control operation panel 23 installed on the front of the main body 29 of the apparatus. Each temperature range can be set according to the heat resistance characteristics of the untreated parts.

In addition, the wire conveyor 9 shown in FIG. 10 is divided from the preheating section A to the reflow section B into a conveyor exclusively for the preheating section A and a conveyor exclusively for the reflow section B, and each conveyor is operated at different speeds. An example showing a case where the operation is performed by a driving source, that is,
At the transition point between the preheating section A and the reflow section B, the 11th
Pulleys 25, 25' for each wire as shown in the figure
A group of pulleys 25 are rotatably supported on a single shaft, and pulleys 26 and 27 for guiding the wire are pivotally mounted on the sides of the pulley 25, and the pulleys 25' and 25' are connected to each other. The wires constituting the conveyor 9 of the preheating section A and the conveyor 28 of the reflow section B are hung alternately to constitute two independent conveyors.

The present invention is constructed as described above.Next, a series of operations of the present invention will be explained.The thermal properties of the substrate 5 of the unprocessed component D shown in FIG. The temperatures of the preheating section A, reflow section B, etc. are set in advance according to each heat resistance of the component 8, and after confirming that the predetermined temperature has been reached, the unprocessed component D is inserted from the component inlet 40 of the device main body 29. When the part D is placed on the wire conveyor 9 and sent, in this case, the part D is supported astride the wires that make up the conveyor 9, and is first guided into the preheating section B in that state, where it is heated. Upper heater 12 and lower heater 1 until passing
Heated by 0.11.

That is, the upper surface of component D is connected to heater 12 and fan 1.
It is heated by blowing hot air generated by 3. In this case, the hot air is blown through the rectifying plate 14, so there is no turbulence in the hot air that is blown from the top toward the conveyor 9 in the preheating section A, so that the entire flow is unidirectional. The temperature distribution for each unprocessed part D on the conveyor 9 is uniform, and the lower surface of the unprocessed part D is heated by a far-infrared heater 10 and a sheathed heater 11.

Therefore, in the preheating section A, the unprocessed parts D are heated in a temperature range that does not cause the cream solder 7 to soften and melt, and on the premise that the board 5 does not soften or deform.
etc., to give untreated parts a condition suitable for heat treatment in the next step.

That is, as shown in FIG. 4, the cream solder is preheated to the temperature of part A (150°C) in the softening/melting temperature characteristic diagram, and the heat generated by the heater 24 and fan 18 provided in the upper part in the reflow part B is generated. By further passing the hot air near the infrared heater 17, the additionally heated hot air is blown onto the unprocessed part D, while the lower surface of the article D is exposed to the radiant heat from the infrared heater 15 disposed opposite to the lower part of the conveyor 9. Therefore, the cream solder 7' is heated at the same time to rapidly raise the temperature to the temperature of part B (200°C) in the above characteristic diagram, and is rapidly melted to melt and adhere the cream solder 7' between the conductive pattern 6 and the chip component 8, thereby creating an electrical connection. After being mechanically integrated, immediately after exiting the reflow section B, it is rapidly cooled with air in the cooling section C.

That is, in the cooling C, the cold air taken in from the outside by the fan 19 is blown toward the conveyor 9 from the ventilation path a formed by the guide plate 20, so that the cold air easily passes between the parts and blows onto the conveyor 9. The air enters the lower part, passes between them again, is guided to the ventilation path b, and is removed by the Morotsuko fan 21 to the outside of the main body of the apparatus. In other words, parts in the cooling section
Since D' passes through a flow of cold air taken in from the outside by the fan 19, it is rapidly cooled and taken out from the outlet 41 as a finished product D'.

In the thus obtained product D', the cream solder 7' is completely fused to the conductive pattern 6 and the chip part 8, as shown in FIG.

The cream solder shown in Figure 4 is called eutectic solder, and exhibits characteristics with two temperature ranges; first, it exhibits a constant value for a certain period of time at a temperature of 150℃, and then it exhibits a constant value for a certain period of time at a temperature of 200℃. Solder has a temperature characteristic in which it melts when a certain period of time passes at a high temperature. Therefore, it is necessary for the above-mentioned eutectic solder to provide adaptive conditions of temperature and time corresponding to these two temperature ranges. For this reason, in the present device, in the preheating section A, appropriate conditions are provided by the feeding speed of the conveyor 9 and the infrared heaters 10 and 12 to accommodate the solder in the A section, and in addition, in the reflow section B, the solder is melted. The heaters 15, 17, and 24 provide the required temperature.

The device of the present invention described above shows a case that best matches the temperature characteristics of eutectic solder, but like the eutectic solder described above, it can also be used with solder that has two temperature ranges but with different temperature values and exposure times. , or for low-temperature soldering where the temperature is constant throughout, it is necessary to provide an atmosphere that adapts to these temperature conditions, and the temperature can be adjusted for each part, but the time is determined by the preheating part A and reflow part B in the above device. Therefore, in the apparatus of the present invention, the conveyors 9 and 28 are dedicated to the preheating section and the reflow section, respectively, as shown in FIG. By circulating through the drive line and freely changing the speed of each conveyor 9, 28, the feeding speed of the preheating section and reflow section can be changed according to the type of solder, and the exposure time suitable for each type of solder can be adjusted. It is possible to obtain.

Normally, it is not possible to connect two conveyors at the connection part with a completely flat surface without recessed grooves. In other words, it is impossible to arrange the guide pulleys of two different conveyors on the same axis, so two pulleys are used.As a result, a depressed groove corresponding to the diameter of the pulley is created, which makes it difficult to smoothly move the parts to be processed. This can be alleviated to some extent by reducing the diameter of the pulley to reduce the depression groove, but it cannot be said to be perfect, and if the diameter of the pulley is reduced, the drive line In any case, it was essentially impossible to achieve perfection, as the load on the system increased.

Therefore, in the present invention, since the connecting portions of two conveyors constituted by a plurality of linear rows are supported by a plurality of concentrically supported pulley groups, there is no depression groove at the connecting portions of both conveyors. It is suitable for transporting small parts, and the exposure time between the preheating section and the reflow section can be freely changed, and it can easily adapt to solders having different temperature characteristics.

Since the solder is melted within the heat-resistant temperature range without applying an excessive heat load to the chip components or the board material, soldering can be performed quickly without causing thermal damage to the chip components.

By using a conveyor made of multiple wires, the heat capacity of the present invention can be almost ignored, unlike the conventional conveyor made of plate materials, and the heat radiation from the heater to unprocessed parts can be efficiently received. Because it is made of strips, no dust gets on it, and even if there is dust, it has no effect at all, unlike conventional heat conduction. Because the board is different from the conventional one, the board does not warp along the board surface, and the rectifier plate guides hot air from the fan in one direction and blows it toward the conveyor, reducing heat turbulence. Since there is no flow and the surface of the conveyor can be heated evenly, preheating of unprocessed parts and melting and heating of solder can be uniformly performed without any corners.

Furthermore, by making the above-mentioned conveyor into a wire material, which is the most characteristic feature of the present invention, it is possible to connect two or more conveyors in one plane, and the circulation speed can be made completely different for each belt, so it is possible to use different types of solder. In order to provide the most suitable conditions, the exposure time can be adjusted by changing the passing speed of the preheating section and reflow section according to the conditions.If it is necessary to take a long exposure time, a furnace with a long length is required. However, in the present invention, since this point passing speed can be freely adjusted, it is possible to downsize the device.

Furthermore, in the cooling section, a fan blows cold air onto the product to rapidly cool it down and take it out, removing harmful resin gases etc. mixed into the cream solder generated in each preheating section A and reflow section B. It has many excellent features not found in conventional equipment, such as opening the damper and exhausting completely through the duct, which prevents pollutants from scattering into the workplace atmosphere, helping to preserve the working environment. This is a device suitable for mass production.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a conventional device, Fig. 2 is a schematic side view of another conventional example, Fig. 3 is a schematic side view of a conventional example other than the above two examples, and Fig. 4 is a temperature characteristic diagram of eutectic solder. , FIG. 5 is a vertical cross-sectional view of the untreated part, FIG. 6 is a vertical cross-sectional view of the processed part, FIG. 7 is a front view of the device of the present invention, FIG. 8 is a right side view of the same device, and FIG. 9 is a vertical cross-sectional view of the unprocessed part. 10 is a partial front view showing a modified example of the conveyor section of the proposed device; FIG.
The figure is a perspective view of the main parts of the same conveyor section. 9... Wire conveyor, 11... Sheathed heater, 12... Heater, 14, 16... Current plate, 2
8...Conveyor, 29...Device body, 36...Power source, A...Preheating section, B...Reflow section, C...
Cooling section.

Claims (1)

[Claims] 1 A preheating section A and a reflow section B that blow hot air generated by a fan and a heater toward a lower heating source through a honeycomb-shaped rectifier plate.
, a cooling section C that takes in outside air and blows it onto the object to be processed, a wire conveyor consisting of a plurality of linear sections installed horizontally independently between the left and right sides of the apparatus main body via each of the above sections; A conveyor comprising an exhaust device for removing gas generated from cream solder, and configured to carry out soldering processing by sequentially transporting objects to be processed to each of the above-mentioned processing sections by means of a wire conveyor. type heat treatment equipment.